GY 112L Earth History
Lab 10
The Mesozoic: Part One
GY 112L Instructors:
Douglas Haywick, James Connors,
Mary Anne Connors
Department of Earth Sciences,
University of South Alabama
Fifth Edition: August 2009©
The Fine Print
Contents of these lab exercises are the intellectual property of the authors, particularly Dr. Doug Haywick. Contents cannot be
reproduced outside of the University of South Alabama “family” (faculty and students) without the permission of D. Haywick.
Internet users can seek this permission by contacting Dr. Haywick through the web address provided below.
This manual is constantly being updated and occasionally, even improved. Typos, grammatical errors and sections that make no
sense whatsoever may, or may not, be intentional. If you find an error, show it to your instructor. You may get bonus points.
More likely you will be told to go away
The recipes that are included in some sections are intended to prove that you can eat anything as long as you serve it with plenty
of ketchup. Neither Haywick, nor the Connors are responsible for any food poisoning that might occur if you actually try them.
http:/www.southalabama.edu/geology/haywick
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Lab Ten
The Mesozoic, Part One: Fish, Plants and Alabama Stratigraphy
Background: Finally, we make it to the Mesozoic. That wonderful Era that spans the time
interval between two of the Earth's most memorable extinctions (the Permian-Triassic event
and the Cretaceous - Tertiary event). You will get a chance to see some Mesozoic rocks
from Alabama, but the majority of the lab will focus on some very important fossil groups
left over from the Paleozoic (i.e., they first evolved in the Paleozoic). For the first time, we
will examine some fossils that belong to the phylum Chordata. The beasties we will be
looking at are collectively referred to as vertebrates and they all contain some sort of a
backbone and central nervous system. The chordates, which include humans, dogs, cats,
bears, etc., are an enormous group of beasties. The mammals that we typically associate
with the chordates really did not take off as a group until the end of the Mesozoic; however,
there were plenty of other chordates in the Paleozoic (possibly even earlier), and most of
these have geological relevance. In GY 112L, we will consider the following important
chordates: the fish, the amphibians and the reptiles. The reptiles will comprise part of the
last lab in this course (Week 12), but we will focus on the fish and amphibians today. In this
lab we will also look at several plant fossils (Kingdom: Plantae).
The rock suite consists of Mesozoic rocks of Alabama. Some are important rock units at the
surface; others are known only from the sub-surface (they are obtained through coring,
usually in pursuit of petroleum and natural gas reservoirs). The Smackover Formation (subsurface) is the most important rock unit for petroleum/natural gas production in the state. The
offshore production platforms that you see scattered around Dauphin Island and Mobile Bay
are usually either targeting the Smackover Formation or the Norphlet Formation that
underlies it. Both are more than 20,000 feet below the water's surface.
And as an extra bonus for today’s lab only…. It’s double recipe day.
Don’t forget to label and to put scales on all of your diagrams.
Figure shows some Jurassic and Triassic plant fossils. From Le Conte, J., 1905. Elements of Geology. D.
Appleton & Co. New York, 667p.
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The Vertebrates (Phylum Chordata)
The Fish: The first true chordates evolved in the early Cambrian or upper-most Proterozoic
(Figure 10-1). Fish, those animals with backbones that swim in oceans, also evolved in the
Cambrian, but the first fish were relatively primitive. They belonged to the class Agnatha, a
group of animals that are jawless. There was only one order of these animals during the
Cambrian and Ordovician (order Ostercondermata) and they were pretty weird animals
(Figure 10-2a). A living example of this type of beastie is the lamprey☼, a nasty animal that
attaches itself to the body of another fish with rows of teeth that line its mouth. It literally
sucks the vital juices right out of the host fish. During the Early Silurian, three more orders
of Agnathians appeared, but more importantly, the first jawed fishes also evolved. It is
thought that bone-supported jaws evolved from some sort of gill support system, but there is
little fossil evidence to prove this one way or another. The acanthodians were the first class
of jawed fish. Some call them "spiny sharks". They were generally quite small, had paired
fin-spines and a "heterocercal" tail (where the backbone curves upward and the fin is
developed downward; Figure 10-2b). By the Late Silurian, jawed fishes had evolved into two
large classes; the chondricthyes (sharks, rays and other fishes with cartilaginous skeletons)
and the osteichthyes (fishes with bony skeletons like catfish, trout, bass and grouper etc).
Both of these classes are still around today, but the osteichthyes are by far the most
successful of the lot. Most modern fish belong to the subclass Actinopterygii and are
characterized by fins that are supported by parallel cartilaginous rods.
Not all fish classes were as successful as the osteichthyes. One group (order Placodermata)
is thankfully extinct. The placoderms were armored fish that were very abundant during the
Devonian. In fact, the Devonian is called the age of the fishes in part because of the presence
of the placoderms. Placoderms may have been related to the sharks, but they were unique in
that they had a series of stony plates around their heads (Figure 10-2c). These plates must
have provided excellent defense from predators (Figure 10-2d). Nevertheless, they died off
relatively quickly (by the end of the Mississippian).
Figure 10-1: Evolution of the fish. From Moody, R., 1980. Prehistoric World Chartwell
Books. New Jersey, 320p.
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Figure 10-2: Representative fish of many extant and extinct classes and orders. From
Moody, R., 1980. Prehistoric World Chartwell Books. New Jersey, 320p. A: Agnathids; B:
acanthodians; C, D: placoderms.
As far as we can tell, all of these fishes had gills by which to remove oxygen from water. In
the Early Devonian, some bony fish were beginning to evolve rudimentary lungs. The
Rhipidistians eventually evolved into the lungfish☼. There was also another important
development underway. Some rhipidistians were beginning to develop modified fin supports
that consisted of small bones. Two types appeared (1) ray fins and (2) lobed fins (Figure 103). The addition of lungs and bone-supported fins heralded a major evolutionary transition.
Soon fish would not be solely restricted to the aquatic environment. They were about to
move onto the land. They were about to evolve into amphibians.
The Amphibians: The first amphibian was Ichthyostega sp. (Figure 10-4). It looked pretty
much like a rhipidstian fish called Eusthenopteron and most paleontologists believe that fish
like this were the immediate ancestors of the first amphibians. Ancient rhipidstian fish like
coelacanths☼ lived in freshwater environments and it is not unreasonable to envision that
some found themselves trapped in gradually drying pools of water. Well if you had lungs and
strong fins, you'd be able to crawl to the next water pool. Those that were strongest survived
to reproduce. Wimps died off. Evolution is an amazing process that still provides scientists
with surprises. Take the coelacanth for example. This fish has not changed much in outward
appearance since the Cretaceous (or earlier), but modern species are now fully marine and
have apparently lost their lungs (maybe they smoked too many cigarettes!). Moreover, they
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Figure 10-3: Ray and lobed fins, a new development in fin structure in Paleozoic
rhipidistians. From Moody, R., 1980. Prehistoric World Chartwell Books. New Jersey, 320p.
now live in very deep marine environments. They were not rediscovered until the 1930's.
Prior to this, they were considered extinct. Surprise again.
Ichthyostega first appeared in the Late Devonian. As with all amphibians, it had to spend a
considerable amount of time in the water. Modern amphibians have very porous skin that
easily dehydrates. They must also reproduce by laying eggs in an aquatic environment. You
might ask yourself what happens if the environment starts to dry up? Well as it turns out, the
world climate did dry considerably after the end of the Pennsylvanian Period. Pangaea was
in the process of forming and as we discussed in class, much of the interior started getting
arid. If you were an amphibian that needed water to lay your eggs in, you were in trouble. It
was time to evolve into a new group of animals that were less dependant on water. That
group of animals were the reptiles. You will learn more about these animals in an upcoming
lab and/or in a GY 112 lecture.
Figure 10-4: Ichthyostega; the first reptile. From Moody, R., 1980. Prehistoric World
Chartwell Books. New Jersey, 320p.
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Kingdom Plantea
The organisms that comprise the plant kingdom can trace their ancestors well back into the
Archean. Stromatolites, although not plants in the strictest sense, share several characteristics
with plants (e.g., photosynthesis). The first “true” plants were probably the algae. There are
several types of these plants. Green Algae (Division* Chlorophyta☼) contain chlorophyll
and were around in the earliest Cambrian. Some evidence suggests that they had might have
evolved in the Late Proterozoic. Brown Algae (Division Phaeophyta) and Red Algae
(Division Rhodophyta) lack chlorophyll but are nevertheless equally important groups of
plants. All three divisions first appeared in marine environments and are still found there
today. Coralline green algae such as Halimeda sp. and Penicillus sp. are exceptionally
important in modern tropical environments and produce much of the unconsolidated
sediment found in and around reefs. Coralline red algae☼ is equally important in colder
water (temperate) shelf environments. The main thing to note is that the first plants were
marine, but over time, plants developed traits that would prove invaluable for a major
invasion of the terrestrial parts of the Earth.
The fossil record suggests that the first terrestrial plants began to colonize the Earth in the
Silurian (Figure 10-5). These plants were small and very simple consisting of little more than
reproductive pods (sporangia) atop of short, equally branching stems. These plants are
called psilopsids (Division Psilophyta) and are typified by Cooksonia spp. This genus was
seedless, primitively vascular and devoid of any leaves. Reproduction took place via
dispersion of spores similar to what we see today in mushrooms and many other fungi. It is
likely therefore that these plants required standing water or soggy soil to grow and
reproduce. Paleobotanists have found evidence suggesting that the psilopsids possessed an
underground anchor system called a rhizome☼. This is not exactly a root system. It is more
Figure 10-5: Evolution of the major terrestrial plant divisions. From Wicander, R. and
Monroe, J.S., 1993. Historical Geology. West Publishing, 640 p.
*
Botanists use divisions in place of phyla.
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like an underground horizontal stem which stores food and water. New plants tend to bud
from the rhizome. Although not quite roots, rhizomes did allow the psilopsids to grown erect
and support themselves against wind, gravity and flowing water.
Despite the primitive nature of the psilopsids, the development of a vascular system was a
major evolutionary advance for it allowed water and nutrients to be carried from the ground
upward into the stems and sporangia. Prior to this, plants had to be small in order to stay in
contact with their water and food supplies. From this point onward in geological time, plants
could start to grow large. By the Devonian, there were great forests across the face of the
Earth’s land masses.
The Devonian was a time of drastic evolution of plant types. The pteridophytes (Division:
Pteridophyta) were fernlike, vascular plants that had leaves (sometimes very tightly packed
close to the plant’s trunk) and reproduced via spores. Unlike the psiloposids, the spores were
generally underneath the leaves rather than at the tips of the stems which probably provided
a bit more protection to the reproductive cells of the plants. Their reproductive cycle may
also have been more complex possibly involving an intervening underground
prothallus/gametophyte stage. Gametophytes are underground “sub-plants” that produce
spore-producing generations of plants (called sporophytes).
There are several different varieties of pteridophytes. They include the lycopsids, the
sphenopsids and the pteropsids. Between the lecture on plants and this background lab
information, you are probably maxed out by plant taxonomy. So perhaps it is time to start
using more common plant names to help you comprehend all of these data. The most
common living lycoposids are the club mosses, a very “simple” plant with small “simple”
leaves. Fossil examples of this plant class include Lepidodendron sp. ☼, quite possibly the
most easily identifiable plant in Earth history. It had a classic “diamond-shape” pattern on
the bark (which were the tree’s leaves) and for this reason, they are called the “scale trees”.
Lepidodendron reached over 30 m in height.
The most common modern sphenopsids are the horsetails. Fossils of this class include
Annularia sp. and Calamites sp. Both of these genera also have diagnostic characteristics
(particularly in the arrangement of needle-like leaves) which you will soon discover in the
lab exercises.
Pteropsids are a class of plants which have gaps between their leaves. They include true ferns
(there is a group of ferns that bore seeds to reproduce – they are NOT pteropsids). True ferns
date back to the Devonian and grew to heights that would equal many modern trees. Tall
ferns like this still exist in temperate rain forests along western Canada (especially
Vancouver Island) and New Zealand and are well worth examining if you ever get the
chance to go to those places.
The next major evolutionary shift in the plants again had to do with reproduction. The plants
were still too tied to locations near permanent supplies of water. What was really needed was
a means by which to distribute plants a LONG way from the parent. Enter the gymnosperms
(Division Pinophyta). This large group, also known as the “naked seed” plants, began to
dominate the plant world by the middle Paleozoic. Their mode of reproduction was to
produce two types of spores. One was very small and was able to be dispersed by the wind.
Today we call it pollen. In some gymnosperms, the remaining larger spores (now called
seeds) were encased in separate male and female cones. Reproduction depended upon the
arrival of pollen on the wind which mean that new plants could be distributed over much
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larger areas.
There were many classes of gymnosperms, and most still have living representatives around
today. One very important exception are the pterospermophytes or seed ferns. They
evolved in the late Devonian, but were extinct by the middle Mesozoic. The other classes
include cycadophyta (the cycads), gingkophyta (the ginkos) and coniferophyta (the
conifers). You can find plants of each of these classes adjacent to the Life Sciences Building
(and at Dr. Haywick’s house), and if you have a good imagination, you can almost visualize
what it was like in the Mesozoic. But keep an eye open for hungry Tyranosauruses. They
were another Mesozoic dweller.
Another significant development in the plant world occurred during the middle to late
Mesozoic. Plants began to produce flowers and “enclosed seeds” as part of the reproduction
cycle. The benefit now afforded to the angiosperms (Division Magnoliophyta☼) was twofold. Plant embryos were contained in a nutrient rich (and quite frequently tasty) host. The
seed (the embryo plus the endosperm or food store) was produced through a “double
fertilization” process. Pollen entering the flower fertilize the ovum (producing the seed) and
also fused with the wall of the ovum to produce the endosperm. The whole seed is protected
by a coating or peel (e.g., apple peel).
The flowers also attracted insects which proved to be a vital ally in reproduction. Insects did
the same job as the wind in dispersing pollen, but they were much more focused in their
activities. Bees fly from flower to flower. The wind disperses pollen everywhere (including
our lungs – Mobile in the spring is not a good place to live because of conifer pollen).
It is unbelievable just how successful the angiosperms have been on this planet. In little less
than 100 million years, they have absolutely dominated the terrestrial plant world (Figure 106). In comparison, the pteridophytes and the gymnosperms have declined in importance.
Figure 10-6: Taxonomic turnover during the Phanerozoic. From Niklas K.J.,1997. The
Evolutionary Biology of Plants. University of Chicago Press, Chicago, IL.
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Doug's Most Excellent* Australian Angiosperm Encased Seed Soup
(AKA Australian Pumpkin** (Squash) Soup)
Serves: The amount of soup you produce in this recipe is sufficient to feed most
of the Earth's Population
2 or 3 medium butternut squashes (about 5 pounds total weight)
4 large ripe tomatoes
1 large ripe mango
3 large onions
2 pints heavy cream (or substitute no fat half and half)
3-6 vegetable stock cubes
2 tbs dill weed
salt and pepper to taste
1 bottle of Australian Shiraz wine
Open the bottle of wine. Decant or otherwise let it breathe for 30 minutes.
Meanwhile, peel and de-seed the squash. This job really sucks and if you are like
me, you will cut off at least two fingers during this step. That’s okay. The
blood adds necessary iron to your diet and you have a nice bottle of pain killer
sitting on the table. Speaking of which, have a drink of wine. Cut the peeled
squash into wedges and put in a large stock pot. Blanch the tomatoes in hot water
and then immerse them in cold water. The skin should easily slide off. Remove it
and add the tomatoes to the stock pot with the squash. Peel and coarsely chop the
onion. The best approach for doing this is to first have a drink of wine then add
the onions to the stock pot. Add enough water to cover the squash, onions and
tomatoes. Add the stock cubes, cover the pot and bring to a rolling boil. Reduce
heat and simmer for 30 -40 minutes or until the squash is really mushy. Allow to
cool, then puree the pot's entire contents through a food processor. This will
take a while, so have a drink of wine. Peel and de-seed the mango and then puree
the fruit with one of the last aliquots of squash. Mix this in with the rest of
the pureed soup. Re-heat almost to the boil. Add 1½ pints of heavy cream, pepper,
dill weed, and if necessary (check first!), salt. Ladle soup into individual
bowls and swirl in a few tablespoons of cream into each just before serving. Have
a drink of wine. You earned it.
* This is my single most requested recipe from friends and colleagues who all
claim it is a "most excellent" soup.
** Australians seem to think that anything melon-shaped is a "pumpkin", including
butternut squash, spaghetti squash, acorn squash and Rosanne Barr.
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Baked Osteichthyes au Gratin ala Newfoundland served with a side
of Nova Scotia Pteropsida Tips
Serves 4
2 fillets of cod, red snapper or grouper(skinned and de-boned)
1 package frozen Pteropsida Tips (better known as fiddle heads*)
2 cups of shredded old cheddar cheese
¼ cup shredded Parmesan cheese
2 medium onions
8 oz sliced mushrooms
2 cups milk (1% or skim)
4 tbs butter or margarine
3 tbs corn flour
½ lemon
1 chilled bottle of Riesling (New Zealand, Oregon or Canadian
varieties. Stay away from any Riesling from California)
Did you know that fish is good for you? Yep. You deserve a reward for treating
your body so well tonight. Open the Riesling. Have a drink of wine. Preheat your
oven to 325˚F then extract the fish from its wrappings. Rinse it in water, pat it
dry and put aside. Get a medium sized sauce pan. Peel and finely dice the onions.
Put them in the pot. Add the butter and heat over medium heat until the onions
are nice and golden. Add the mushrooms and corn flour and mix well. The butter
should quickly absorb into the flour leaving a semi solid mass. Before this goop
burns, add the milk and mix like your life depends on it. In a while you will
find that the milk mixture has thickened up. If it has, have a drink of wine. If
not; no wine for you! Start over. Add 1½ cups of the shredded cheese to the milk
mixture and mix until it is well blended. Place ¼ of this mixture on the bottom
of a greased baking dish. Place the fish on top of this base. Squeeze the juice
of ½ lemon over the fish and then cover it with the rest of the milk-cheese
mixture. Sprinkle the remaining grated cheddar over the milk/cheese mixture. Then
do the same with the parmesan cheese. After all. You can never have too much
cheese. Hey, you know what goes well with cheese? Wine! Why not have a drink of
wine? Bake the fish uncovered at 325˚F for 30 minutes or until cooked.
While the fish is baking, cook up the fiddle heads. Follow the instructions on
the package. Usually, this involves boiling the crap out of them. I recommend
adding a bit of lemon juice to the water before you start boiling them. Once
cooked, drain them, pat them dry and add a good dollop of butter just before
serving. That was pretty easy wasn't it? This leaves plenty of time for a drink
of wine!
*Fiddle Heads are the tops of edible ferns and are a delicacy in the Maritime
Provinces of Canada, especially Nova Scotia. Your odds of finding fresh ones in
Mobile are not good, but I did once pick up a few packages from the Fresh Market
on Airport Blvd. They really are yummy even without a bottle or Riesling.
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